[SOLVED] Change the number of steps in various volume controls

Apologies for the ambiguous title, not enough characters available.

On my XFCE 4.12 system I use both a keyboard special keys: XF86VolUp and XF86VolDown, and the mouse wheel hovering over xfce4-pulseaudio-plugin to change the volume on my system. The problem is that the volume level has to be quite low to be non-intrusive and this exposes that the volume increments are too coarse and its either too loud or too quiet. The steps either from the keyboard or the mouse wheel are consistent, so they are both probably acting on the volume level in the same way.

Using the slider in xfce4-pulseaudio-plugin I can adjust the sound to a level that works, but if I want to turn it up for a quiet song or down, and use the keyboard or mouse wheel the step is to big - and opening the slider and adjusting the slider is too slow.

Is there a way to increase the number of increments/reduce the size of each volume increment in the volume control?

In the settings editor XFCE4-Mixer appears to have the exact parameter "volume-step-size", but it does nothing - probably because I'm not using it.